Method of Viscosity Control

ABSTRACT

This invention relates to a method of lubricating an internal combustion engine comprising at least one of a crankcase, a gear and a wet-clutch, said method comprising supplying to said crankcase, gear and wet-clutch a lubricating composition comprising: (a) an oil of lubricating viscosity; and (b) a viscosity modifier with a number average molecular weight from 1000 to 75,000, wherein the lubricating composition has a SAE viscosity grade from XW-Y, wherein X is from 0 to 20 and Y is from 20 to 50; and wherein the lubricating composition has a phosphorus content from a metal hydrocarbyl dithiophosphate of 0.12 wt % or less.

FIELD OF INVENTION

The present invention relates to a method of viscosity control bylubricating an internal combustion engine comprising at least one of acrankcase, a gear, and a wet-clutch with a lubricating composition.

BACKGROUND OF THE INVENTION

It is well known for lubricating oils to contain a number of additivesused to protect the engine from wear and provide viscosity control.Common additives for engine lubricating oils include zincdialkyldithiophosphate (ZDDP) an antiwear additive. It is believed thatZDDP antiwear additives protect the engine by forming a protective filmon metal surfaces. Viscosity modifiers with a number average molecularweight above 100,000 are known in crankcase applications as viscositymodifiers because they help control high temperature viscometrics inmulti-grade lubricants. Viscosity modifiers in various applications areknown from, e.g., U.S. Pat. No. 5,112,509.

Current and future government legislation regulating exhaust emissionsfrom internal combustion engines that contain exhaust treatment devicesare requiring a reduction in the phosphorus and metal content of engineoils used in these engines. This reduction in the phosphorus and metalcontent of engine oils is being implemented because it is thought thatthey can adversely affect the performance of exhaust treatment devices.

However, any reduction in the performance of catalytic converters causedby phosphorus poisoning tends to result in increased amounts ofgreenhouse gases such as nitric oxide and/or ash formation. Furthermore,reducing the amount of ZDDP will increase the amount of wear in anengine crankcase.

In an internal combustion engine with a wet-clutch (e.g. a 4-strokemotorcycle engine) legislation regulating exhaust emissionsaffects/restricts the amount of emissions. However, as the internalcombustion engine has a common oil reservoir, the oil must be suitablefor a crankcase application and a gear, a transmission system or aclutch mechanism which all have higher operating conditions resulting ina severe wear environment. Therefore removing antiwear chemistry, suchas, a phosphorus containing compound will tend to increase the amount ofwear in the gear, transmission or clutch. If a conventional crankcaseviscosity modifier (with a number average molecular weight of 100,000 ormore) is employed in combination with reduced amounts of antiwearchemistry, it is believed that surface film break down due to theviscosity modifier shear will give rise to increased wear. The surfacefilm break down is believed to be due to reduction in high temperatureviscosity of a lubricating oil proportional to the rate of shear of theviscosity modifier.

It would be advantageous to have a method of viscosity control for aninternal combustion engine with a wet-clutch capable of imparting atleast one of wear control, acceptable fuel economy, acceptable hightemperature viscometrics and increased lubricant oil service drains. Thepresent invention provides a method of viscosity control for saidinternal combustion engine and capable of imparting at least one of wearcontrol, acceptable fuel economy, acceptable high temperatureviscometrics and increased lubricant oil service drains.

SUMMARY OF THE INVENTION

This invention provides a method of lubricating an internal combustionengine comprising a crankcase and at least one of a gear and awet-clutch, said method comprising supplying to said crankcase and to atleast one of the gear and wet-clutch a lubricating compositioncomprising: (a) an oil of lubricating viscosity; and (b) a viscositymodifier with a number average molecular weight from 1000 to 75,000,wherein the lubricating composition has a SAE viscosity grade from XW-Y,wherein X is from 0 to 20 and Y is from 20 to 50; and wherein thelubricating composition has a phosphorus content from a metalhydrocarbyl dithiophosphate of 0.12 wt % or less.

DETAILED DESCRIPTION OF THE INVENTION

This invention provides a method of lubricating an internal combustionengine comprising a crankcase and at least one of a gear and awet-clutch, said method comprising supplying to said crankcase and to atleast one of the gear and wet-clutch a lubricating compositioncomprising: (a) an oil of lubricating viscosity; and (b) a viscositymodifier with a number average molecular weight from 1000 to 75,000,wherein the lubricating composition has a SAE viscosity grade from XW-Y,wherein X is from 0 to 20 and Y is from 20 to 50; and wherein thelubricating composition has a phosphorus content from a metalhydrocarbyl dithiophosphate of 0.12 wt % or less.

Internal Combustion Engine

The internal combustion engine of the invention typically comprises acrankcase, a gear and a wet-clutch. Optionally the internal combustionengine further comprises a manual or automatic transmission. In oneembodiment the gear is from a gearbox.

As used herein the term “wet-clutch” is known to a person skilled in theart as meaning one that contains a clutch plate(s) that is bathed orsprayed by a lubricant, e.g., that of the transmission, and thelubricating oil gets between the plate(s).

In one embodiment the internal combustion engine has a common oilreservoir supplying the same lubricating composition to the crankcaseand at least one of a gear and a wet-clutch. In certain embodiments thelubricating composition is supplied to the crankcase and to the gear (ormultiplicity of gears), or to the crankcase and the wet clutch, or tothe crankcase and both the gear (or gears) and the wet clutch.

In one embodiment the internal combustion engine is a 4-stroke engine.In one embodiment the internal combustion engine is also referred togenerically as a small engine.

The small engine in one embodiment has a power output of 2.24 to 18.64kW (3 to 25 horsepower (hp)), in another embodiment 2.98 to 4.53 kW (4to 6 hp) and in another embodiment exhibits 100 or 200 cm³ displacement.Examples of small engines include those in home/garden tools such aslawnmowers, hedge trimmers, chainsaws, snow blowers or roto-tillers.

In one embodiment the internal combustion engine has a capacity of up to3500 cm³ displacement, in another embodiment up to 2500 cm³ displacementand in another embodiment up to 2000 cm³ displacement. Examples ofsuitable internal combustion engines with a capacity up to 2500 cm³displacement include motorcycles, snowmobiles, jet-skis, quad-bikes, orall-terrain vehicles. In one embodiment the internal combustion engineis a tractor or other agricultural vehicle such as a combined harvester.

In one embodiment the internal combustion engine is not a tractor orother agricultural vehicle. In another embodiment the internalcombustion engine does not contain a dry-clutch i.e. a system thatseparates the engine from the transmission such as a transmission on anautomotive vehicle. In another embodiment the internal combustion engineis not suitable for use with a diesel fuel.

In one embodiment the internal combustion engine is suitable formotorcycles for example motorcycles with a 4-stroke internal combustionengine.

Oil of Lubricating Viscosity

The lubricating composition includes natural or synthetic oils oflubricating viscosity; oil derived from hydrocracking, hydrogenation orhydrofinishing; and unrefined, refined and re-refined oils, and mixturesthereof.

Natural oils include animal oils, vegetable oils, mineral oils andmixtures thereof. Synthetic oils include hydrocarbon oils, silicon-basedoils, and liquid esters of phosphorus-containing acids. Synthetic oilsmay be produced by Fischer-Tropsch gas-to-liquid synthetic procedure aswell as other gas-to-liquid oils. In one embodiment the polymercomposition of the present invention is useful when employed in agas-to-liquid oil. Often Fischer-Tropsch hydrocarbons or waxes may behydroisomerised.

In one embodiment the base oil is a polyalphaolefin (PAO) including aPAO-2, PAO-4, PAO-5, PAO-6, PAO-7 or PAO-8 (the numerical value relatingto Kinematic Viscosity at 100° C.). The polyalphaolefin in oneembodiment is prepared from dodecene and in another embodiment fromdecene. Generally, the polyalphaolefin suitable as an oil of lubricatingviscosity has a less than that of a PAO-20 or PAO-30 oil, the reasonbeing that a polyalphaolefin with a viscosity higher than a PAO-30 istypically too viscous for effective lubrication of an internalcombustion engine.

Oils of lubricating viscosity may also be defined as specified in theAmerican Petroleum Institute (API) Base Oil InterchangeabilityGuidelines. In one embodiment the oil of lubricating viscosity comprisesan API Group I, II, III, IV, V, VI oil or mixtures thereof, and inanother embodiment API Group II, III, IV oil or mixtures thereof. Inanother embodiment the oil of lubricating viscosity is a Group III or IVbase oil and in another embodiment a Group IV base oil. If the oil oflubricating viscosity is an API Group II, III, IV, V or VI oil there maybe up to 40 wt % and in another embodiment up to a maximum of 5 wt % ofthe lubricating oil an API Group I oil present.

In one embodiment the lubricating composition has a SAE viscosity gradefrom XW-Y, wherein X is from 0 to 20 and Y is from 20 to 50.

In one embodiment X is chosen from 0, 5, 10, 15 or 20.

In one embodiment Y is chosen from 20, 25, 30, 35, 40, 45 or 50.

The oil of lubricating viscosity in one embodiment is present from 2 wt% to 99.5 wt % of the lubricating composition, in another embodimentfrom 29 wt % to 98.25 wt % of the lubricating composition and in anotherembodiment from 40 wt % to 97 wt % of the lubricating composition.Examples of suitable amounts of an oil of lubricating viscosity include55 wt %, 60 wt %, 65 wt %, 70 wt %, 75 wt % or 80 wt %.

Viscosity Modifier

The viscosity modifier of the invention includes at least one of thefollowing polymers such as:

-   -   (a) polyalkenes or derivative thereof (such as polyisobutene,        olefin copolymers such as ethylene-alpha-olefin copolymers or        ethylene-propylene polymers);    -   (b) polyalphaolefins (which can be a type of polyalkene (a));    -   (c) alpha-olefin-unsaturated carboxylic reagent copolymers;    -   (d) poly(meth)acrylates;    -   (e) interpolymers derived from the polymerisation of a vinyl        aromatic monomer and an unsaturated carboxylic acid or        derivatives thereof; and    -   (f) mixtures thereof.

The viscosity modifier in one embodiment is present from 0.5 wt % to 95wt %, in another embodiment 0.75 wt % to 70 wt % and in anotherembodiment 1 wt % to 40 wt % of the lubricating composition. Examples ofa suitable amount of viscosity modifier include 8 wt %, 10 wt %, 12 wt%, 14 wt %, 16 wt %, 18 wt %, 20 wt %, 22 wt %, 24 wt %, 30 wt %, 35 wt%, or 55 wt %.

The viscosity modifiers (which may also be dispersant viscositymodifiers, as further described below) are known in the art andcommercially available from a number of corporations, including TheLubrizol Corporation, Degussa AG and Rohmax GmbH.

In one embodiment the viscosity modifier has a Shear Stability Index(SSI) as determined by CEC L-45-A-99 of 22 or less, 20 or less or 18 orless. In one embodiment the viscosity SSI is 2 or more or 4 or more.Examples of suitable ranges of SSI include 2 to 22 or 4 to 18.

In one embodiment the viscosity modifier has a number average molecularweight from 1000 to 75,000, in another embodiment 2000 to 60,000, inanother embodiment 6000 to 50,000 and in another embodiment 8000 to40,000. In one embodiment the viscosity modifier has a number averagemolecular weight from 1000 to 20,000 and in another embodiment from25,000 to 40,000. In one embodiment the dispersant viscosity modifierhas a number average molecular weight that is the same as the rangesgiven for the viscosity modifier.

In one embodiment the viscosity modifier is a dispersant viscositymodifier. The polymeric dispersant viscosity modifier may be derivedfrom a functionalised polyolefin, an esterified polymer derived from:(i) a vinyl aromatic monomer; and (ii) an unsaturated carboxylic acid orderivatives thereof; or mixtures thereof.

Poly(meth)acrylates

In one embodiment the viscosity modifier can be a poly(meth)acrylatewith a number average molecular weight of 10,000 to 35,000, 12,000 to20,000 or 25,000 to 35,000.

In one embodiment the poly(meth)acrylate viscosity modifier includescopolymers of (i) a methacrylic acid ester containing 9 to 30 carbons inthe ester group, (ii) a methacrylic acid ester containing 7 to 12carbons in the ester group wherein the ester group contains a 2-(C₁₋₄alkyl)-substituents and optionally (iii) at least one monomer selectedfrom the group consisting of a methacrylic acid ester containing from 2to 8 carbon atoms in the ester group and which are different frommethacrylic acid esters used in (i) and (ii) above. A more detaileddescription of polymethacrylate viscosity modifiers can be found in U.S.Pat. No. 6,124,249.

In one embodiment the viscosity modifier is a functionalizedpoly(meth)acrylate. The poly(meth)acrylate is functionalized with anitrogen containing monomer thus forming a dispersant viscositymodifier. In one embodiment the nitrogen containing monomer isincorporated into the poly(meth)acrylate through standardcopolymerization techniques. The nitrogen containing monomer includes avinyl substituted nitrogen heterocyclic monomer, a dialkylaminoalkyl(meth)acrylate monomer, a dialkylamino alkyl (meth)acrylamide monomer, atertiary-(meth)acrylamide monomer and mixtures thereof. The alkyl groupscan contain 1 to 8, or from 1 to 3 carbon atoms. In one embodiment, thedispersant viscosity modifier is a poly(meth)acrylate.

Useful nitrogen containing monomers include vinyl pyridine, N-vinylimidazole, N-vinyl pyrrolidinone, and N-vinyl caprolactam,dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate,dimethylaminobutylacrylamide dimethylamine propyl methacrylate,dimethylaminopropylacrylamide, dimethylaminopropylmethacrylamide,dimethylaminoethylacrylamide, tertiary butyl acrylamide or mixturesthereof.

The poly(meth)acrylate polymeric dispersant viscosity modifier includesa copolymer derived from a (meth)acrylate monomer containing an alkylgroup with 1 to 30 carbon atoms, in another embodiment 1 to 26 carbonatoms and in another embodiment 1 to 20 carbon atoms. The alkyl groupincludes mixtures derived from an alcohol containing 1 to 4 carbonatoms, 8 to 10 carbon atoms, 12 to 14 carbon atoms, 12 to 15 carbonatoms, 16 to 18 carbon atoms or 16 to 20 carbon atoms. Examples ofcommercially available alcohol mixtures include the following productssold under the brand names of Dobanol™ 25, Neodol™ 25, Lial™125, andAlchem™ 125. In one embodiment the alcohol is a single alcohol, i.e.,not a mixture.

The (meth)acrylate monomer includes those derived from natural orsynthetic sources. When derived by synthetic sources the (meth)acrylatemonomer may be prepared using known direct esterification and/ortransesterification processes.

In one embodiment the poly(meth)acrylate polymeric dispersant viscositymodifier is derived from a methyl (meth)acrylate monomer and at leastone other (meth)acrylate monomer including an alkyl group with 8 to 20carbon atoms, in another embodiment 10 to 18 carbon atoms and in anotherembodiment 12 to 15 carbon atoms. The methyl (meth)acrylate monomer isin the range from 1 wt % or more of the poly(meth)acrylate, in anotherembodiment in the range from 8 wt % or more of the poly(meth)acrylateand in another embodiment in the range from 10 wt % or more of thepoly(meth)acrylate. Upper limits on the amount of methyl (meth)acrylateinclude 40 wt % of the poly(meth)acrylate, in another embodiment 30 wt %of the poly(meth)acrylate and in another embodiment 20 wt % of thepoly(meth)acrylate.

Polyalphaolefins

In one embodiment the viscosity modifier can be one or morepolyalphaolefins having a kinematic viscosity at 100° C. from 40 mm/s(cSt) to 100 mm/s (cSt). In one embodiment a polyalphaolefin viscositymodifier is PAO-40, PAO-50, PAO-60 or PAO-80. In one embodiment thepolyalphaolefin's number average molecular weight is from 1400 to 2000.Generally the polyalphaolefin viscosity modifier is too viscous to beconsidered as an oil of lubricating viscosity.

In one embodiment the olefin copolymers have a number average molecularweight of 14,500 to 70,000.

Interpolymers

In one embodiment the viscosity modifier can be a polymeric dispersantviscosity modifier such as an esterified polymer derived from monomerscomprising: (i) a vinyl aromatic monomer; and (ii) an unsaturatedcarboxylic acid or derivatives thereof. The polymer prior toesterification is generally referred to as an interpolymer. In oneembodiment the esterified polymer is substantially free of to free of a(meth)acrylate ester. In one embodiment the interpolymer is astyrene-maleic anhydride copolymer. In one embodiment the esterifiedpolymer contains a nitrogen derived from a nitrogen containing compoundcapable of reacting with a functionalised polymer backbone to form anamidated polymer.

The molecular weight of the interpolymer may also be expressed in termsof the “reduced specific viscosity” of the polymer which is a recognizedmeans of expressing the molecular size of a polymeric substance. As usedherein, the reduced specific viscosity (abbreviated as RSV) is the valueobtained in accordance with the formula RSV=(RelativeViscosity−1)/Concentration, wherein the relative viscosity is determinedby measuring, by means of a dilution viscometer, the viscosity of asolution of 1 g of the polymer in 10 cm³ of acetone and the viscosity ofacetone at 30° C. For purpose of computation by the above formula, theconcentration is adjusted to 0.4 g of the interpolymer per 10 cm³ ofacetone. A more detailed discussion of the reduced specific viscosity,also known as the specific viscosity, as well as its relationship to theaverage molecular weight of an interpolymer, appears in Paul J. Flory,Principles of Polymer Chemistry, (1953 Edition) pages 308 et seq. In oneembodiment the interpolymer polymer of the invention has a RSV in therange of 0.05 to 2 in another embodiment 0.06 to 1, in anotherembodiment 0.06 to 0.8 and in another embodiment 0.07 to 0.2. In anotherembodiment the RSV is 0.12. In one embodiment the interpolymer numberaverage molecular weight is 10,000 to 40,000.

Examples of a vinyl aromatic monomer include styrene (often referred toas ethenylbenzene), substituted styrene or mixtures thereof. Substitutedstyrene monomers include functional groups such as a hydrocarbyl group,halo-, amino-, alkoxy-, carboxy-, hydroxy-, sulphonyl- or mixturesthereof. The functional groups include those located at the ortho, metaor para positions relative to the vinyl group on the aromatic monomer,the functional groups are located at the ortho or para position beingespecially useful. In one embodiment the functional groups are locatedat the para position. Halo-functional groups include chlorine, bromine,iodine or mixtures thereof. In one embodiment the halo functional groupis chlorine or mixtures thereof. Alkoxy functional groups may contain 1to 10 carbon atoms, in another embodiment 1 to 8 carbon atoms, inanother embodiment 1 to 6 carbon atoms and in yet another embodiment 1to 4 carbon atoms. Alkoxy functional groups containing 1 to 4 carbonatoms is referred to as lower alkoxy styrene.

The hydrocarbyl group includes ranges from 1 to 30 carbon atoms, inanother embodiment 1 to 20 carbon atoms, in another embodiment 1 to 15carbon atoms and in yet another embodiment 1 to 10 carbon atoms.Examples of a suitable hydrocarbyl group on styrene monomers includealpha-methylstyrene, para-methylstyrene (often referred to as vinyltoluene), para-tert-butylstyrene, alpha-ethylstyrene, para-lower alkoxystyrene or mixtures thereof.

In one embodiment the alpha-olefin-unsaturated carboxylic reagentcopolymer has a number average molecular weight of 15,000 to 40,000.

Polyalkene or Derivatives Thereof

In one embodiment, the viscosity modifier is a polyalkene or derivativesthereof. In one embodiment the polyalkene or derivative thereof can havea number average molecular weight of 2300 to 25,000. The polyalkeneincludes homopolymers and interpolymers of olefins having from 2 to 40,or from 3 to 24, or from 4 to 12 carbon atoms. The olefins may bemonoolefins, such as ethylene, propylene, 1-butene, isobutene, analpha-olefin, or polyolefinic monomers, including diolefinic monomerssuch 1,3-butadiene and isoprene. The alpha-olefins generally have from 4to 30, or from 8 to 18 carbon atoms. These olefins are sometimesreferred to as mono-1-olefins or terminal olefins. The alpha-olefins andisomerized alpha-olefins include 1-octene, 1-nonene, 1-decene,1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene,1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 1-heneicosene,1-docosene, and 1-tetracosene. Commercially available alpha-olefinfractions that can be used include the C15-18 alpha-olefins, C12-16alpha-olefins, C14-16 alpha-olefins, C14-18 alpha-olefins, C16-18alpha-olefins, C16-20 alpha-olefins, C18-24 alpha-olefins, and C22-28alpha-olefins. The polyalkenes may be prepared by conventionalprocedures. The polyalkenes are described in U.S. Pat. Nos. 3,219,666and 4,234,435. Examples of polyalkenes include polypropylenes,polybutylenes, polyisoprene and polybutadienes. In one embodiment, thepolyalkene is a homopolymer, such as a polyisobutene. One example of auseful polybutene is a polymer where 50% of the polymer is derived fromisobutylene.

In another embodiment, the viscosity modifier is anethylene-alpha-olefin copolymer. Typically, the copolymer is a randomcopolymer. The copolymer generally has from 30% to 80%, or from 50% to75% by mole of ethylene. The alpha-olefins include butene, pentene,hexene or one more of the above-described alpha-olefins. In oneembodiment, the alpha-olefin contains from 3 to 20, or from 4 to 12carbon atoms. In one embodiment, the ethylene-alpha-olefin copolymershave a number average molecular weight from 800 to 6000, or from 1500 to5000, or from 2000 to 4500. Examples of ethylene alpha-olefinscopolymers include ethylene-butene copolymers and ethylene-octenecopolymers. Examples of commercially available copolymers includeLucant™ HC 600 and Lucant™ HC 2000 (Mw=25,000), available from MitsuiPetrochemical Co. Ltd.

In another embodiment, the viscosity modifier is an ethylene propylenepolymer. These polymers include ethylene propylene copolymers andethylene propylene terpolymers. When the ethylene propylene polymer isan ethylene propylene copolymer (EPM, also called EPR polymers), it maybe formed by copolymerization of ethylene and propylene under knownconditions such as Ziegler-Natta reaction conditions. In one embodimentthe ethylene propylene copolymer contains units derived from ethylene inan amount from 40 mol % to 70 mol %, or from 50 mol % to 60 mol %, or 55mol %, the remainder being derived from propylene.

In another embodiment, the ethylene propylene polymer is a terpolymer ofethylene, propylene and a diene monomer. In one embodiment, the diene isa conjugated diene. The dienes are disclosed above. The terpolymers areproduced under similar conditions as those of the ethylene propylenecopolymers. The preferred terpolymers contain units derived formethylene in amount from 10% to 80%, or from 25% to 85%, or 35% to 60% bymole, and units derived from propylene in amount from 15% to 70%, orfrom 30% to 60% by mole, and units derived from diene third monomer inamount from 0.5% to 20%, or from 1% to 10%, or 2% to 8% by mole.

In one embodiment the polyalkene or derivatives thereof is a dispersantviscosity modifier. Typically a dispersant viscosity modifier frompolyalkene or derivatives thereof is prepared by the reaction of (a) apolyalkene; (b) an acylating agent such as maleic anhydride; and (c) anamine.

The amine includes a monoamine, a polyamine or mixtures thereof. Theamine includes primary functionality, secondary functionality ormixtures thereof. The amine includes cyclic, linear or branchedstructures, and examples include an alkylenemonoamine, a heterocyclicmonoamine, an alkylenepolyamine, a heterocyclic polyamine or mixturesthereof. In one embodiment the amine contains not more than one primaryor secondary amino group, for example N,N-dimethylaminopropylamine.

In one embodiment the amine may be a hydroxy-substituted hydrocarbylamine such as a hydroxyalkyl amine. Examples of a suitablehydroxy-substituted hydrocarbyl amine include aminoethyl ethanolamine,aminopropyl ethanolamine, aminobutyl ethanolamine or mixtures thereof.

In one embodiment the amine includes compounds that are represented bythe formula:

wherein

w is the number of R¹ atoms, including ranges from 4 to 16 atoms, inanother embodiment 5 to 12 atoms, and in another embodiment 5 to 8atoms;

y is the number of carbon atoms associated with R², including rangesfrom 1 to 8, in another embodiment 1 to 6, and in another embodiment 2to 5 carbon atoms;

R¹ is independently an atom including carbon, oxygen, nitrogen,phosphorus or mixtures thereof;

R² is an alkyl or an alkenyl group with containing y carbon atoms,especially useful examples of R² including ethyl, propyl or mixturesthereof; and

R³ and R⁴ are independently hydrogen or a hydrocarbyl group; in anotherembodiment at least one is hydrogen, and in another embodiment both arehydrogen.

When R³ or R⁴ is a hydrocarbyl group, the number of carbon atoms presenttherein is in the range from 1 to 8, in another embodiment in the rangefrom 1 to 5 and in another embodiment in the range from 1 to 3. Examplesof a hydrocarbyl group include methyl, ethyl, propyl, butyl, pentyl ormixtures thereof.

Formula (I) represents a compound that includes a mononuclear cyclicstructure, a polynuclear cyclic structure or mixtures thereof. Whenformula (I) represents a mononuclear structure, w in one embodimentranges from 5 to 8 and in another embodiment 6 to 7. When formula (I)represents a polynuclear cyclic structure w in one embodiment rangesfrom 8 to 16 and in another embodiment 10 to 12. The cyclic ringincludes aromatic, non-aromatic or mixtures thereof, although anon-aromatic ring is especially useful.

Suitable cyclic amines include 4-amino diphenyl amine,4-(3-aminopropyl)morpholine, 4-(2-aminoethyl)morpholine or mixturesthereof. In one embodiment the cyclic amine is4-(3-aminopropyl)morpholine or mixtures thereof.

Metal Hydrocarbyl Dithiophosphate

In one embodiment of the invention the composition further contains ametal hydrocarbyl dithiophosphate. The amount of the metal hydrocarbyldithiophosphate present is enough to provide a phosphorus content in thelubricating composition from said metal hydrocarbyl dithiophosphate of0.12 wt % or less.

In one embodiment the phosphorus content in the lubricating compositionfrom a metal hydrocarbyl dithiophosphate is below 0.1 wt %, in anotherembodiment below 0.085 wt %, in another embodiment below 0.06 wt % orlower. In one embodiment the lower limit of the phosphorus content inthe lubricating composition from a metal hydrocarbyl dithiophosphate is0 ppm or higher, in another embodiment 50 ppm or higher, in anotherembodiment 125 ppm or higher and in another embodiment 200 ppm orhigher. Examples of suitable ranges include 50 ppm to 0.1 wt % or 125ppm to 0.085 wt %.

Examples of a metal hydrocarbyl dithiophosphate include zincdihydrocarbyl dithiophosphates (often referred to as ZDDP, ZDP or ZDTP).In one embodiment the number of carbon atoms of each hydrocarbyl groupis 2 to 30, 3 to 14 or 4 to 10.

Examples of suitable zinc hydrocarbyl dithiophosphates compounds mayinclude those with a hydrocarbyl group of octyl, 2-ethylhexyl,methylpentyl-isopropyl. 2-ethylhexyl-isopropyl, pentyl-isobutyl ormixtures thereof.

Additional Performance Additives

In one embodiment of the invention the composition optionally includesat least one additional performance additive. The additional performanceadditive includes at least one of metal deactivators, detergents,dispersants, extreme pressure agents, antiwear agents, antioxidants,corrosion inhibitors, foam inhibitors, demulsifiers, pour pointdepressants, friction modifiers, seal swelling agents and mixturesthereof. In one embodiment the additional performance additives may beused alone or in combination.

In one embodiment the total combined amount of the other performanceadditive compounds present ranges from 0 wt % to 30 wt %, in anotherembodiment from 1 wt % to 25 wt % and in another embodiment 2 wt % to 20wt % or from 3 wt % to 10 wt % of the lubricating composition. Althoughone or more of the other performance additives may be present, it iscommon for the other additional performance additives to be present indifferent amounts relative to each other.

If the present invention is in the form of a concentrate (which may becombined with additional oil to form, in whole or in part, a finishedlubricant), the ratio of the various additives to the oil of lubricatingviscosity and/or to diluent oil include the ranges of 80:20 to 10:90 byweight.

Friction modifiers include fatty amines, esters such as borated glycerolesters, fatty phosphites, fatty acid amides, fatty epoxides, boratedfatty epoxides, alkoxylated fatty amines, borated alkoxylated fattyamines, metal salts of fatty acids, fatty imidazolines, condensationproducts of carboxylic acids and polyalkylene-polyamines, amine salts ofalkylphosphoric acids, molybdenum dithiocarbamate or mixtures thereof.Antioxidants include sulphurised olefins, hindered phenols,diphenylamines. Detergents include neutral or overbased, Newtonian ornon-Newtonian, basic salts of alkali, alkaline earth and transitionmetals with one or more of a phenate, a sulphurised phenate, asulphonate, a carboxylic acid, a phosphorus acid, a mono- and/or adi-thiophosphoric acid, a saligenin, an alkylsalicylate, a salixarate ormixtures thereof. Dispersants include N-substituted long chain alkenylsuccinimide as well as post-treated versions thereof. Post-treateddispersants include those further treated by reaction with materialssuch as urea, boron, thiourea, dimercaptothiadiazoles, carbondisulphide, aldehydes, ketones, carboxylic acids,hydrocarbon-substituted succinic anhydrides, nitriles, epoxides andphosphorus compounds.

Antiwear agents include compounds such as metal thiophosphates,especially zinc dialkyldithiophosphates; phosphoric acid esters or saltthereof; phosphites; and phosphorus-containing carboxylic esters,ethers, and amides; antiscuffing agents including organic sulphides andpolysulphides, such as benzyldisulphide, bis-(chlorobenzyl)disulphide,dibutyl tetrasulphide, di-tertiary butyl polysulphide,di-tert-butylsulphide, sulphurised Diels-Alder adducts or alkylsulphenyl N′N-dialkyl dithiocarbamates. Extreme pressure (EP) agentsincluding chlorinated wax, organic sulphides and polysulphides, such asbenzyldisulphide, bis-(chlorobenzyl)disulphide, dibutyl tetrasulphide,sulphurised methyl ester of oleic acid, sulphurised alkylphenol,sulphurised dipentene, sulphurised terpene, and sulphurised Diels-Alderadducts; phosphosulphurised hydrocarbons, metal thiocarbamates, such aszinc dioctyldithiocarbamate and barium heptylphenol diacid; may also beused in the composition of the invention.

Additional performance additives such as corrosion inhibitors includeoctylamine octanoate, condensation products of dodecenyl succinic acidor anhydride and a fatty acid such as oleic acid with a polyamine; metaldeactivators including derivatives of benzotriazoles, thiadiazoles suchas dimercaptohtiadiazole and its derivatives, 1,2,4-triazoles,benzimidazoles, 2-alkyldithiobenzimidazoles or2-alkyldithiobenzothiazoles; foam inhibitors including copolymers ofethyl acrylate and 2-ethylhexylacrylate and optionally vinyl acetate;demulsifiers including polyethylene glycols, polyethylene oxides,polypropylene oxides and (ethylene oxide-propylene oxide) polymers; pourpoint depressants including esters of maleic anhydride-styrene,polymethacrylates, polyacrylates or polyacrylamides; and seal swellagents including Exxon Necton-37™ (FN 1380) and Exxon Mineral Seal Oil(FN 3200); may also be used in the composition of the invention.

The following examples provide an illustration of the invention. Theseexamples are non exhaustive and are not intended to limit the scope ofthe invention.

EXAMPLES Example 1 and Reference Examples 1-2

Lubricating compositions are prepared by blending additives as shown inTable 1 into a 10W-40 lubricant. The lubricating compositions have aphosphorus content in the lubricating composition from a metalhydrocarbyl dithiophosphate of less than 0.12 wt %. The compositionsprepared are:

TABLE 1 Number Average Example Polymer Type Molecular Weight REF1Commercially available Over 100,000 Olefin copolymer REF2 Commerciallyavailable 84,000 Olefin copolymer EX1 Polymethacrylate 15,000

Viscosity Test

A viscosity test to determine Shear Stable Index (SSI) is carried outemploying (i) a KRL Rig at 80° C. for 20 hours and the methodology ofCEC L-45-A-99; and (ii) separately an Orbahn™ Rig and the methodology ofCEC-14-A-93_(—)30. Generally, better results are obtained for exampleswith lower percentage reductions in viscosity. Further acceptableresults are obtained when the percentage loss in viscosity is 12% orless. The results obtained are shown in Table 2.

TABLE 2 SOT/ EOT % Loss SSI SSI Example ——— — KRL Rig—— ——/ (Orbahn)REF1 KV₁₀₀ 14.96 7.94 46.93 76 25  KV₄₀ 98.2 48.50 50.61 — — REF2 KV₁₀₀11.86 10.30 13.15 26 0 KV₄₀ 77.39 65.52 15.34 — — EX1 KV₁₀₀ 12.72 11.688.18 14 0 KV₄₀ 83.60 75.35 9.87 — — Footnote to Table 2, SOT is definedas Start of Test; and EOT is defined as End of Test and “—” representsunmeasured values.

The results indicate that the presence of the viscosity modifier with anumber average molecular weight from 1000 to 75,000 has acceptable shearstability and is suitable for viscosity control in an internalcombustion engine comprising a crankcase and at least one of a gear anda wet-clutch. Further, the viscosity modifier is capable of imparting atleast one of wear control, acceptable fuel economy, acceptable hightemperature viscometrics and increased lubricant oil service drains.Furthermore, the results indicate that a polymer with a low ShearStability Index of 26 and a number average molecular weight of above75,000 provides poor a viscosity control performance.

In this specification the terms “hydrocarbyl substituent” or“hydrocarbyl group,” as used herein are used in its ordinary sense,which is well-known to those skilled in the art. Specifically, it refersto a group primarily composed of carbon and hydrogen atoms and attachedto the remainder of the molecule through a carbon atom and which doesnot exclude the presence of other atoms or groups in a proportioninsufficient to detract from the molecule having a predominantlyhydrocarbon character. In general, no more than two, in one aspect nomore than one, non-hydrocarbon substituent will be present for every tencarbon atoms in the hydrocarbyl group; typically, there will be nonon-hydrocarbon substituents in the hydrocarbyl group. A more detaileddefinition of the terms “hydrocarbyl substituent” or “hydrocarbylgroup,” is provided in U.S. Pat. No. 6,583,092.

As used herein the term poly(meth)acrylate and other generic stems with(meth)acryl means polymethacrylate, polyacrylate or other acryl ormethacryl moieties.

Each of the documents referred to above is incorporated herein byreference. Except in the Examples, or where otherwise explicitlyindicated, all numerical quantities in this description specifyingamounts of materials, reaction conditions, molecular weights, number ofcarbon atoms, and the like, are to be understood as modified by the word“about.” Unless otherwise indicated, each chemical or compositionreferred to herein should be interpreted as being a commercial gradematerial which may contain the isomers, by-products, derivatives, andother such materials which are normally understood to be present in thecommercial grade. It is to be understood that the upper and loweramount, range, and ratio limits set forth herein may be independentlycombined.

Similarly, the ranges and amounts for each element of the invention maybe used together with ranges or amounts for any of the other elements.

1. A method of lubricating an internal combustion engine comprising a crankcase and at least one of a gear and a wet-clutch, said method comprising supplying to said crankcase and to at least one of said gear and wet-clutch a lubricating composition comprising: (a) an oil of lubricating viscosity; and (b) a viscosity modifier with a number average molecular weight from about 1000 to about 75,000, wherein the lubricating composition has a SAE viscosity grade from XW-Y, wherein X is from 0 to about 20 and Y is from about 20 to about 50; and wherein the lubricating composition has a phosphorus content from a metal hydrocarbyl dithiophosphate of 0.12 wt % or less, wherein the internal combustion engine is a 4-stroke motorcycle engine.
 2. The method of claim 1, wherein the internal combustion engine has a common oil reservoir supplying the same lubricating composition to the crankcase and at least one of a gear and a wet-clutch.
 3. The method of claim 1, wherein the lubricating composition is supplied to the crankcase and to the gear (or multiplicity of gears).
 4. The method of claim 1, wherein the lubricating composition is supplied to the crankcase and the wet clutch.
 5. The method of claim 1, wherein the lubricating composition is supplied to the crankcase and both the gear (or gears) and the wet clutch.
 6. The method of claim 1, wherein the viscosity modifier includes at least one of: (a) polyalkenes or a derivative thereof; (b) polyalphaolefins; (c) alpha-olefin-unsaturated carboxylic reagent copolymers; (d) poly(meth)acrylates; (e) Esterified interpolymers derived from the polymerisation of a vinyl aromatic monomer and an unsaturated carboxylic acid; or (f) mixtures thereof.
 7. The method of claim 1, wherein the viscosity modifier has a number average molecular weight 2000 to 60,000, or 8000 to 40,000.
 8. The method of claim 1, wherein the viscosity modifier has a number average molecular weight from 1000 to 20,000, or from 25,000 to 40,000.
 9. The method of claim 1, wherein the viscosity modifier is a poly(meth)acrylate.
 10. The method of claim 9, wherein the viscosity modifier is a functionalized poly(meth)acrylate.
 11. The method of claim 10, wherein the poly(meth)acrylate is functionalized with a nitrogen containing monomer.
 12. The method of claim 1, wherein the viscosity modifier is present from 0.5 wt % to 95 wt %, or from 1 wt % to 40 wt % of the lubricating composition.
 13. The method of claim 1, wherein the viscosity modifier has a Shear Stability Index (SSI) as determined by CEC L-45-A-99 of 22 or less.
 14. The method of claim 1, wherein the viscosity modifier has a Shear Stability Index (SSI) as determined by CEC L-45-A-99 of 4 to
 18. 15. A method of lubricating a 4-stroke motorcycle internal combustion engine comprising a crankcase and at least one of a gear and a wet-clutch, said method comprising supplying to said crankcase and to at least one of said gear and wet-clutch a lubricating composition comprising: (a) an oil of lubricating viscosity; and (b) a poly(meth)acrylate viscosity modifier with a number average molecular weight from about 1000 to about 75,000, wherein the lubricating composition has an SAE viscosity grade from XW-Y, wherein X is from 0 to about 20 and Y is from about 20 to about 50; and wherein the lubricating composition has a phosphorus content from a metal hydrocarbyl dithiophosphate of 0.12 wt % or less. 